Pulse oximetry is the means of determining the percentage of oxygen in a person’s blood. Since oxygen is crucial to human life, checking oxygen levels is a vital sign a doctor must take. That is why wearables like smart watches now have the technology to measure this vital health reading.
Smart watches track peripheral oxygen saturation because it is a useful indicator of the blood’s oxygen level over time. SpO2 measurement is a widely used technique for determining the degree to which oxygen is diffused throughout the circulatory system. Even though arterial oxygen saturation (SaO2) gives more accurate results, it can’t check continuous blood oxygen as it requires testing a blood sample.
You can’t use SaO2 for continuous blood oxygen monitoring because it requires drawing and testing a blood sample. Therefore, SpO2 is the “gold standard” for pulse oximetry because it is the most convenient and useful option.
The measurement of blood oxygen level is based on the different properties of oxygenated and deoxygenated blood. Blood that is low on oxygen appears dark red, while oxygenated blood appears bright red. This coloring difference is because blood with more oxygen reflects red light more strongly, while blood with less oxygen absorbs red light more strongly.
Overview
Have you heard of SpO2 sensors, pulse ox, and blood oxygen levels in your search for a new smart watch? Blood oxygen saturation (SpO2) sensors quantify the amount of oxygen in your blood. Indeed, most modern smart watches and fitness trackers incorporate these sensors and metrics. One limitation is that not all wearables manufacturers integrate these sensors.
While some smart watches do this automatically while you sleep, others allow you to measure your blood oxygen saturation levels manually. This article will explore how SpO2 sensors function and what their limitations are. We’ll also discuss the specifics of configuring some of the most well-liked wearables for SpO2 monitoring.
How SpO2 Sensors Work
Pulse oximeters – small devices that measure the amount of oxygen in your blood – are something you may already be familiar with. As low oxygen levels were a common symptom of many people with COVID-19, these devices gained popularity in the early stages of the pandemic. Since then, pulse oximeters have become indispensable.
Smart watches have SpO2 sensors that work the same way as PPG sensors, which are used to measure blood pressure. Green light shined into your skin by optical sensors that measure your heart rate can be useful in making a pulse photogram. The SpO2 sensors in smart watches emit red and infrared light into your skin instead of green light. Next, an algorithm is used to estimate your blood oxygen levels based on how the light is reflected.
Importance of SpO2 Sensors in Smart Watches
Even though research findings have been positive, certain experts are still determining the usefulness of these health sensors. Some think the blood oxygen sensors in wearables like the Apple Watch are most beneficial when used regularly. That is because they provide more context about overall wellness.
That doesn’t mean professionals in the medical field don’t see the potential of these sensors. One big difference between smart watches and standard pulse oximeters is that smart watches are always on your wrist. Smart watches can measure blood oxygen levels automatically as a background function throughout the day.
With a traditional pulse oximeter, you can’t check the amount of oxygen in your blood while you sleep. However, Fitbit, Samsung, Garmin, and Apple devices can do so passively. Apple and Garmin both can take blood oxygen readings at regular intervals.
Despite being able to take scans in the background, smart watches can only measure SpO2 levels while the wearer is at rest. Apple’s background measurements occur when the wearer isn’t moving. On the other hand, Garmin takes readings less frequently if it detects high movement.
Although smart watches weren’t designed for medical diagnosis, they provide more insights you can take to the doctor for examination. Here are the other benefits.
Respiratory Illness
A blood oxygen sensor could help those with asthma or other breathing conditions know when to relax. For some time now, blood oxygen levels have proven to be a reliable indicator of COVID-19 illness. If you’re worried about your health, you should talk to a doctor before using a wearable device.
High Altitude Hiking
If you’re a hiker or mountain climber, a smart watch with a built-in blood oxygen sensor can tell you how your body is adjusting to high altitudes. It enables you to keep tabs on progress without carrying extra gear.
Sleep Apnoea
People suffering from sleep apnoea frequently report feeling tired or sleepy throughout the day. The disorder is characterized by shallow breathing or pauses during sleep. Before the development of smart watch blood and oxygen technology, diagnosing sleep apnoea was difficult. Now, however, early detection is easy, cheap, and doesn’t need much effort, thanks to wearable technology.
General Wellbeing
Wearables with a blood oxygen sensor are useful for keeping tabs on wellbeing rather than specific fitness metrics. It can track your oxygen levels and assess how well you’re performing in various physical activities. The knowledge is crucial for both seasoned athletes and fitness newbies.
Limits of Wearable SpO2 Sensors
Manufacturers of wearables have started incorporating these sensors for a variety of reasons. Many researchers now consider it an important indicator of sleep quality. Companies like Fitbit and Withings add SpO2 sensors in their products as a possible way to find out if someone has a sleep disorder.
Fingertip pulse oximeters are a Class II medical device, while the SpO2 features on smart watches are meant for general health. For instance, the accuracy of blood oxygen measurements taken from the wrist is lower than those taken from the fingertip. Unlike fingertip pulse oximeters, which measure oxygen saturation by shining light through your whole finger, wrist sensors determine it by measuring the reflection of light.
In the end, readings from SpO2 monitors that you wear should never be used to make decisions about your health. Avoid placing too much faith in these interpretations; at most, they will give you an insight into where you stand compared to others. Despite this, you should expect varying results on occasion.
Conclusion
Although convenient, smart watches’ reflectance-based oximetry needs to be better established. Also, the accuracy of measuring blood oxygen levels with a smart watch is below what is acceptable in a clinical setting.
The lack of medical certification for these devices shows that the smart watch oximeter is not meant for healthcare. Since its results are often wrong, it is better used in the context of physical fitness. You should not move around too much while your smart watch measures your blood oxygen level (SpO2).